1. Field of the Invention
This invention relates to a torque sensor unit.
2. Description of Related Art
An example of existing torque sensor units is disclosed in Japanese Patent Publication No. Sho 62-27604, entitled xe2x80x9cControl Unit for Hybrid Vehicle.xe2x80x9d
According to FIGS. 11 and 12 of this publication, the torque sensing mechanism includes two coaxial shafts SH1 and SH2; a torsion bar TB connecting one end of the shaft SH1, and one end of the shaft SH2; metallic gears G1, and G2 fixed to opposite ends of the torsion bar TB; magnetic sensors MS1 and MS2 positioned near tooth tops of the gears G1, and G2; and a phase comparator PC receiving AC signals from the magnetic sensors MS1, and MS2. A phase difference xc3x8 of the AC signals from the magnetic sensors MS1 and MS2 varies as the torsion bar TB twists in response to torque. The phase comparator PC can detect torque on the basis of the phase difference xc3x8.
The foregoing torque detecting mechanism is a large torque sensor unit in which the metallic gears G1, and G2 are fixedly attached to the torsion bar TB and the magnetic sensors MS1, and MS2 are disposed around the gears.
It is therefore an object of the invention to provide a compact torque sensor unit.
In order to accomplish the above object, there is provided a torque sensor unit which includes a countershaft; helical gears for providing said countershaft with not only torque but also axial load generated by their mutual engagement; and axial load measuring means disposed coaxially with the countershaft for the purpose of regulating axial movement of the countershaft and measuring the axial load.
The helical gears are attached on the countershaft and generate axial load when they are mutually engaged. The axial load is transmitted via the countershaft to the axial load measuring instruments which are coaxial with the countershaft, and can be measured by the measuring instruments. The axial load is generated in accordance with the torque, and is measured by the measuring instruments coaxial with the countershaft, thereby downsizing the torque sensor unit.
According to the present invention, thrust bearings are interposed between the countershaft and the axial load measuring instruments.
The thrust bearings are effective in reducing frictional resistance in the rotating direction between the countershaft and the axial load measuring instruments. There is no fear that rotational moment caused in response to the rotation of the countershaft acts on the axial load measuring instruments. Therefore, only the axial load acts on the measuring instruments, which can improve detecting precision of the torque sensor unit because noise components are reduced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.